Nerve electrode apparatus



Nov. 17, 1964 1.. P. MCCARTY 3,157,181 NERVE ELECTRODE APPARATUS Filed May 2, 1962 H j INVENTOR. Les/f6 R Mi. Car/y ATTORNEY period of time.

United States Patent O This invention relates generally to biological instruments and, more particularly, to a novel fully insulated nerve electrode apparatus for stimulation or recording purposes.

In the course of physiological and pharmacological experiments, it is often necessary to cut a nerve and to stimulate one of the ends with electrical impulses from a laboratory instrument. Prior to the present invention, nerve electrode apparatus generally failed to perform adequately when immersed in certain liquids such as body fluids or water. This was generally because the casing for the electrode apparatus was not fully hydrophobic near was there much, if any, attempt to adequately insulate electric contact elements. Electric contacts were usually cemented in place and often broke loose after a short Furthermore, prior nerve electrode apparatus has generally been inadequate to securely hold a nerve fiber across electric contacts. It had also been a problem to make nerve electrode apparatus in sizes small enough to fit easily Within body cavities as well as resist tissue reaction for chronic applications.

Accordingly, it is an object of the present invention to provide a nerve electrode apparatus having a range of applications heretofore impractical.

It is a further object of the present invention to provide for novel nerve electrode apparatus which is substantially insulated from surrounding fluids when in use.

It is another object of the present invention to provide a novel nerve electrode apparatus which is capable of being positioned within relatively small animal body cavities.

A still further object of the present invention is to provide a nerve electrode apparatus which insures that an electrical stimulus will be delivered to the nerve alone and not to surrounding structures.

Another object of the present invention is to provide a novel nerve electrode apparatus with electric contacts which will not break loose during or after normal use.

And a still further object of the present invention is to provide a novel nerve electrode apparatus which is substantially small and completely insulated and which is relatively inexpensive.

Briefly then, the present invention relates to novel nerve electrode apparatus of a miniature size and comprises an insulating material molded or otherwise formed around electric contacts. The electric contacts are permitted to have exposed areas along a central channel of the apparatus wherein the central channel is of a size to hold a nerve fiber snugly within the apparatus. The use of an insulating casing and the snug fit of the nerve fiber prevents electrical shorting out in the apparatus. Modifications of the apparatus can receive either a cut nerve, or in certain chronic applications, can receive uncut nerves. The apparatus is inert and thus causes no reaction in body tissues. It also is generally unbreakable and can be heat sterilized. This invention also relates to the method of using this apparatus by stringing the nerve therethrough and clamping the apparatus in place.

Yet additional objects and advantages of the present invention, and its numerous cognate benefits and features are even more apparent and manifest in and by the ensuing description and specification taken in conjunction with the accompanying drawing in which wheresoever possible, like characters of reference designate corresponding "ice material and parts throughout the several views thereof, in which:

FIGURE 1 is an elevational view illustrating an embodiment of the novel electrode apparatus of the present invention located adjacent a body cavity;

FIGURE 2 is an enlarged partial side elevational view of the electrode apparatus as shown in FIGURE 1;

FIGURE 3 is a top plan view of the electrode apparatus as shown in FIGURE 2; and

FIGURE 4 is an isometric partial view of a modified form of the electrode apparatus of the present invention.

Referring more particularly to FIGURES 1 to 3, the electrode apparatus 10 is shown juxtapositioned within a body cavity 12 of an animal tissue 14 and has electric leads 16 and 18 extending therefrom. Apparatus 10 comprises an electrically insulated insulating outer casing 29 having an elongated channel 22 extending longitudinally throughout the length thereof. Casing 20 can have a conical or tapered head portion 23 for ease in anatomical applications described hereinafter. Electric contacts 24- can comprise a pair of silver rings or their equivalent which are soldered to the flexible electric, leads 16 and 18 which, in turn, can be made of copper or the like.

A molding operation is the preferable Way of forming the apparatus 10. In this operation the ring-like electric contacts 24 are positioned on a mandrel-like form (not shown) of approximately the diameter of the channel 22 which, in turn, is then inserted into a mold (not shown) approximately the size of the casing 20. The mold is then filled with a molding material. This molding material can comprise any plastic material or rubber having the proper forming, electrically insulating and inert properties such as, for example, found in silicon rubber, acrylic polymers, polystyrene, epoxy resins and natural or synthetic rubber. It is also possible to employ other non-castable materials such as polymethylmethacrylate if an adequate forming operation can be achieved.

When employing silicon resin, for example, after the rubber-like resin is vulcanized the resulting electrode apparatus, as shown, consists of the two silver electric contacts 24 which are electrically insulated except for their inner circumferences which form the future point of engagement between the electric contacts and the nerve fiber in the channel 22.

In using a nerve fiber an, it is generally cut and one end thereof is tied to a string-like element 28 made of cotton or other like inert fiber which will not react with tissue. The string is fitted through a top opening 39 in the casing 26 giving access to the channel 22. In operation the string-like element 28 is pulled through channel 22 until the nerve fiber 26 lies across electric contacts 24. The pressure of the casing 26 against tissue 14 will positively locate the apparatus with respect to nerve fiber as when a clamp 32 located closely adjacent the far end or bottom 34 of casing 20 is fastened around the protruding end of the string-like element projecting out from bottom 34 of the casing 20. By having the head portion 23 of a tapered configuration it fits snugly within the body cavity 12. The pressure between the clamp 32 and the tissue 14 will thus securely hold the apparatus ill in a clamped position, there being no necessity for pulling the nerve fiber 2d completely through channel 22.

apparatus is that when used in salt solution, the latter could readily surround the electric contacts and sometimes up to 90% of the electrical energy went into hydrolysis of the solution. The present invention substantially prevents such a waste of electrical energy.

Thus it can readily be seen that the size of opening 20 and the channel 22 depends on the size of the nerve being tested. However, despite the almost infinite number of different nerve fiber sizes, most of the work done in any given biological laboratory probably would require no more "than about three different electrode apparatus having various size openings 30 since there is a range of fibers which can be used with any given one of the openings. For example, in one laboratory using smaller animals such as mice and the like, it was found that three apparatus having openings of approximately inch, /s inch and inch diameter, respectively, were quite adequate for all applications. When larger animals such as sheep are used, apparatus having somewhat larger openings are employed. It has been found that since nerve fibers are quite limp they will effectively lie against the electric contacts even if the optimum re lationship between opening diameter and fiber diameter is not completely achieved.

In certain instances, especially chronic applications, even wire leads 16 and can be electrically insulated by use of one of the inert materials discussed previously as, for example, silicon rubber. Such a material is hydrophobic as well as electrically insulating. Connectors 36 can be used to energize leads 16 and 18 to a source of electric potential commonly used with such apparatus, such as any electrical stimulator or battery.

It is also to be understood that the present invention can be employed as an electrical recording apparatus as well as a stimulator if so desired. This can be accomplished by connecting the leads l6 and l?) instead of to a source of electric potential, to electrical recording devices such as oscillographs and oscilloscopes, which are commonly used in biological laboratories for such purposes.

As mentioned briefly previously, it is sometimes important to have an electrical apparatus adapted for use with an uncut nerve, particularly in chronic applications. Modified apparatus 33, as illustrated in FIGURE 4, has such an application. It is substantially similar to apparatus 10, that is with respect to channel 22-, electric contacts 24, and electric leads 16 and 13, etc., except that in addition it contains a generally zig-zag shaped slot 40 extending from the outer surface of the casing 20 directly down to channel 22, and that the contacts are open where the slot 40 joins channel 22. In this instance a nerve fiber 26 is slipped into the slot 4% and pushed inwardly into casing 20 until it slips into channel 22. Once it is in place in channel 22 it is straightened out and thus unable to be readily removed through the zigzag configuration formed by the slot 40. Of course, it is understood that in this application no string or clamp is necessary as employed in apparatus it).

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the claims.

Accordingly, what is claimed as new is:

l. Nerve electrode apparatus comprising a casing formed of a substantially hydrophobic and chemically inert and electrically insulating material, said casing having an elongated channel therethrough of a cross-sectional configuration generally the same as that of a nerve to be placed therein, said channel providing openings at opposite ends of said casing, electric contacts formed in said casing and presenting exposed surfaces in said channel, and means associated with said contacts for conducting electrical impulses thereto and therefrom.

2. Nerve electrode apparatus comprising a generally cylindrically shaped casing formed of a silicon rubber material, said casing having an elongated channel extending throughout the length thereof, said channel being of a generally circular cross-sectional configuration slightly larger than that of a nerve to be placed therein and providing openings at opposite ends of said casing, electric contact rings formed in said casing and presenting exposed surfaces in said channel, and means connected with said rings for conducting electrical impulses thereto and therefrom.

3. Nerve electrode apparatus comprising a casing formed of a substantially hydrophobic and chemically inert and electrically insulating material, said casing having an elongated channel therethrough of a cross-sectional configuration generally the same as that of a nerve to be placed therein, said channel providing openings at opposite cnds of said casing, an elongated zig-zag slot extending from the outer surface of said casing to said channel and cocxtensively therewith, electric contacts formed in said casing and presenting exposed surfaces in said channel, and means associated with said contacts for conducting electrical impulses thereto and therefrom.

4. Nerve electrode apparatus comprising a generally cylindrically shaped casing formed of a silicon rubber material, said casing having an elongated channel extending throughout the length thereof, said channel being of a generally circular cross-sectional configuration slightly larger than that of a nerve to be placed therein, an elongated zig-zag slot extending from the outer surface of said casing to said channel and coextensively therewith, electric contacts formed in said casing and presenting exposed surfaces in said channel, and means connected with said contacts for conducting electrical impulses thereto and therefrom.

5. Nerve electrode apparatus comprising an elongated casing of silicon rubber, elongated channel means extending from end to end of said casing for snugly receiving a nerve fiber within said casing and electric contacts secured within said casing and presenting exposed surfaces for contacting said nerve fiber.

6. Nerve electrode apparatus comprising a body portion of a substantially hydrophobic and chemically inert and electrically insulating material similar to silicon rubber, elongated channel means extending from end to end of said casing for snugly receiving a nerve fiber within said casing, and electric contacts secured within said casing and presenting exposed surfaces for contacting said nerve fiber.

7. Nerve electrode apparatus comprising a generally cylindrically shaped casing formed of a substantially hydrophobic and chemically inert and electrically insulating material, said casing having an elongated channel extending throughout the length thereof, said channel being of a generally circular cross-sectional configuration slightly larger than that of a nerve to be placed therein, an elongated zig-zag slot extending from the outer surface of said casing to said channel and coextensively therewith, electric contacts formed in said casing and presenting exposed surfaces in said channel, and means connected with said contacts for conducting electrical impulses thereto and therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 390,067 Chisholm Sept. 25, 1888 465,949 Roovers Dec. 29, 1891 2,195,019 Bloomheart Mar. 26, 1940 2,208,023 Ellis July 16, 1940 2,827,041 Pierson Mar. 18, 1958 FOREIGN PATENTS 1,032,685 France Apr. 1, 1953 

1. NERVE ELECTRODE APPARATUS COMPRISING A CASING FORMED OF A SUBSTANTIALLY HYDROPHOBIC AND CHEMICALLY INERT AND ELECTRICALLY INSULATING MATERIAL, SAID CASING HAVING AN ELONGATED CHANNEL THERETHROUGH OF A CROSS-SECTIONAL CONFIGURATION GENERALLY THE SAME AS THAT OF A NERVE TO BE PLACED THEREIN, SAID CHANNEL PROVIDING OPENINGS AT OPPOSITE ENDS OF SAID CASING, ELECTRIC CONTACTS FORMED IN SAID CASING AND PRESENTING EXPOSED SURFACES IN SAID CHANNEL, AND MEANS ASSOCIATED WITH SAID CONTACTS FOR CONDUCTING ELECTRICAL IMPULSES THERETO AND THEREFROM. 